EFFECTS OF DOPING WITH RARE-EARTH ELEMENTS ON THE LOW-TEMPERATURE EDGE LUMINESCENCE OF InP.

An investigation was made of the low-temperature (T equals 2 K) edge luminescence of InP prepared by liquid epitaxy and doped with rare-earth elements Gd and Yb. A typical luminescence spectrum of undoped samples, consisting of a line due to neutral D**0X exciton-donor complexes and a donor-acceptor (DA) recombination band, was modified greatly when the molten solution contained even a small amount of a rare-earth impurity (0. 001 at. %). Such an impurity gave rise to a line due to exciton-acceptor A//1**0X complexes, a line due to two-hole transitions involving various acceptors, and a line due to free excitons. Moreover, there was an increase in the intensity of the DA band and of an A**0e band due to recombination of free electrons at neutral acceptors. When the rare-earth impurity concentration exceeded 0. 01 at. %, the spectrum was dominated by radiative transitions involving shallow acceptors. In a certain range of impurity concentrations the electron mobility was considerably higher than the initial value, reaching 6 multiplied by 10**4 cm**2 multiplied by v** minus **1 multiplied by sec** minus **1, and the low-temperature edge luminescence spectra of such samples were very similar to the spectra of 'pure' n-type InP. The effect of annealing of a molten solution containing a rare-earth impurity on the low-temperature edge luminescence spectra was also studied.